2025-07-092025-07-092025-09-30Tagua Navarrete, M.Á., Serrano Reyes, J., Vélez Godiño, J.A. y Jiménez-Espadafor Aguilar, F.J. (2025). Clean and zero-emission urban buses: Compliance with EU regulations and f leet transition in Seville. https://doi.org/10.1016/j.energy.2025.137025.0360-5442https://hdl.handle.net/11441/175173© 2025 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ).The EU public transport sector is dominated by diesel and natural gas buses, but fleet structures are rapidly changing. EU climate laws drive two strategies: one for bus manufacturers and another for public transport operators (PTO), with different timelines. PTOs must progressively replace fleets with clean and zero-emission buses. This paper develops bus replacement strategies aligned with EU standards, focusing on cost minimization and CO 2 emission reduction. Three propulsion technologies (diesel, compressed natural gas, and electric) and two bus types (regular and articulated) are analyzed. The strategies consider acquisition, operational, and service costs, along with CO 2 emissions. The proposed approach, applied over a 10-year period, uses real-word data from Seville (Spain) PTO to meet EU standards for 2025–2035. Operational data allow precise energy demand estimation, considering propulsion, climatization air compressor, and auxiliaries. CO 2 culations show that CNG buses emit 24 % more CO 2 emissions calper km than diesel buses. Optimization results indicate that a CO 2 minimization strategy reduces emissions by 16.3 %, with only a 6.7 % cost increase compared to the minimal-cost strategy.application/pdf20 p.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/EU regulationsCO2 emissionsBattery electric busesCNG busesEnergy consumption of urban busesFleet transitioninfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccesshttps://doi.org/10.1016/j.energy.2025.137025